In today's radio communications networks a number of different technologies are used, such as Long Term Evolution (LTE), LTE-Advanced, 3rd Generation Partnership Project (3GPP) Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. A radio communications network comprises radio base stations providing radio coverage over at least one respective geographical area forming a cell. User equipments (UE) are served in the cells by the respective radio base station and are communicating with respective radio base station over radio bearers. The user equipments transmit data over an air or radio interface to the radio base stations in uplink (UL) transmissions and the radio base stations transmit data over an air or radio interface to the user equipments in downlink (DL) transmissions. Radio bearer here means user plane bearers on Radio Access Network (RAN) level between radio base stations and UEs.
One important aspect with radio communications networks also referred to as wireless networks is to ensure that the radio communications network is simple to deploy and cost efficient to operate. The vision is that the radio communications network shall be self-organizing in as many aspects as possible. Furthermore, good coverage is important when aiming at a mobile broadband experience, both outdoors and indoors. Typically, this coverage is provided via radio base stations covering larger cells, also referred to as macro base stations, with dedicated transport connections, but it is also possible to consider self-backhauling radio base stations also referred to as Relay Nodes (RN) where the same technology is used both for user data between a user equipment and the RN and for the transport connection between the RN and a radio base station with a dedicated transport connection. Backhauling here means the communication between the transport network and the radio base station, and self-backhauling means the communication between the relay and the radio base station.
In LTE-Advanced it has been decided to support “Type 1” RNs. A “type 1” RN comprises some typical characteristics. A “type 1” RN controls one or more cells, each of which appears to the user equipment as a separate cell distinct from the donor cell. The cells have their own Physical Cell ID (PCI) and transmit information on their own synchronization channels, reference symbols etc. In the context of single-cell operation, the user equipment receives scheduling information and Hybrid Automatic Repeat-request (HARQ) feedback directly from the RN and sends information on its control channels to the RN. A “type 1” RN shall appear as a radio base station to legacy user equipments. Thus, the RN is backwards compatible with a radio base station. This means basically that from a user equipment perspective, there is no difference being served by a radio base station or a “type 1” RN.
The RN is connected to the network via a radio interface, called Un interface, to a Donor eNB (DeNB). The DeNB provides backhaul transport for the RN and all the user equipments connected to the RN. The radio protocols used on the Un interface are based on the radio protocols standardized in LTE. There is a “many to many” mapping between UE Evolved Packet System (EPS) bearer and Un radio bearers. This is needed since the RN can at maximum have eight Un radio bearers but can have many more UE EPS bearers depending on how many user equipments are served under the RN.
The detailed mapping of packets from UE EPS bearers to Un bearers in the UL is divided into two steps; First there is a mapping from Quality of Service (QoS) Class Identifier (QCI) associated with the UE EPS bearer to a DiffServ Code Point (DSCP) in the outer Internet Protocol (IP) header of a packet. This mapping is configured by the Operation And Maintenance (OAM) system of the RN. Then there is a mapping from the DSCP to a Un radio bearer with the help of Traffic Flow Templates (TFT) that are signaled from the DeNB to the RN via the Mobility Management Entity (MME) of the RN. This mapping is controlled by the DeNB. The DL mapping is not specified in detail since it is basically internal to the DeNB.
There is currently no support for making it possible to have different radio bearer mapping in the DL in the DeNB for different types of RNs. There is also only limited support for having different bearer mapping in the UL for different RNs, since the RN OAM system can only configure the QCI to DSCP mapping but is not able to configure the mapping between DSCP and Un radio bearers. The OAM system of the relay node is also not able to control the setup and modification of radio bearers, which is controlled by the DeNB. The radio communications network thus shows a nonflexible behavior with a reduced performance as all relay nodes in a cell follow a cell specific mapping.